On my commute this morning I established that my freehub needs replacing. There's obviously something wrong with the ratchet mechanism, because it intermittently refuses to engage.

My existing setup is a Mavic Crossmax rear wheel (circa 1998) which originally hosted a 9spd cassette. However I have been running it with a 4.5mm spacer and a 7spd cassette which has been working fine.

Can I replace the freehub with a 7spd one, or will that simply not work? Is the wheel somehow dished specifically for the 9spd width? Should I instead just buy another 9spd freehub and continue to use the 4.5mm spacer?

I did look on Sheldon's website, but couldn't find this exact scenario.

You might save yourself some money and see if your current hub just needs some cleaning. It only takes a little bit of gunk to make one of the pawls stick...once they all stick, you now longer have a freewheel, you have a push bike. Most hubs are fairly easy to take apart, then some citrus solvent, a light coat of oil, and you are back on your way. (Note: oil around pawls, grease elsewhere...more or less).
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Ken HiattSep 24 '12 at 17:21

Thanks for the tip - I will have to tolerate it for the rest of the week and try cleaning at the weekend. I had assumed they were sealed, but never really looked into it.
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Sir CrispalotSep 25 '12 at 11:38

1 Answer
1

As you suspected, you may not run a 7 speed free hub with a 9 speed hub shell. You will need a new 9 speed free hub, and continue to use the spacer ass you have been.

Hubs are not generically sized. Each model is sized for the number of gears it is expected to work with. Replacing the freehub will mess with your dropout spacing, or the position of the gears in relation to the wheel, or both. It can also prevent the bearing adjustment from working properly.